During the past year, almost 700 peptides have been produced by the Laboratory. Many have been used for defining MHC class I restricted T cell epitopes and for defining the nature of the interaction between peptides and class I molecules. Peptides have also been extensively used for studying MHC class II restricted epitopes and preparing antisera for a large variety of proteins including several B cell specific proteins, human histamine I receptor, membrane associated protein of Crithidia fasciaulata, P. falciparum protein involved in red blood cell invasion, phosphoprotein signaling domains, the vasodilator maxadilan, HIV-Tax, IkapppaB, various vaccinia proteins such as complement control protein, membrane associated protein of Toxoplasma gondii, purinergic receptor, T cell receptors, PLC gamma 1 and 2 enzymes, various protein kinases, DNA replication protein of Epstein-Barr virus, actin I and II of P. falciparum, SIV proteins, rabbit RAG-2 and human FC(epsilon)R1 beta and gamma chains. Peptides have also been used to study the biological activity of ring-finger DNA proteins, HIV proteins (Tat, Rev and TAR), Duffy blood group antigens, a malaria parasite anti-oxidant; an apoptosis associated ceramide-activated threonine protein kinase, and IL1 beta converting enzyme. Peptides have also been used extensively to study T helper and CTL recognition of peptides associated with HIV, toxoplasmosis, myelin basic protein (multiple sclerosis associated), Friend virus, influenza virus, and a large variety of autoimmune disease such as arthritis, gastritis, EAE and myasthenia gravis. Synthetic peptides representing the immunodominant epitopes of p40-TaxI were used to develop an enzyme immunoassay that was specific for detecting HTLV-I anti-tax antibodies and thus can be used to distinguish HTLV-I and HTLV-II infections. Use of a similar peptide based assay showed that patients with HTLV-I-associated myelopathy (HAM) or adult T cell leukemia (ATL) could be distinguished by their differential immune responsiveness to the immunodominant epitopes of the tax and rex proteins suggesting that such responses may relate to pathogenesis. Finally, an extended tax protein that appears to be a unique characteristic of most HTLV-IIb isolates was found to be useful for an immunoassay that could distinguish HTLV-IIa and HTLV-IIb infections.